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A parameter-invariant activity threshold for the erasure of spatial pattern in active Model H

Year: 2026
Type: preprint
Abstract: Solver, sweep scripts and trajectory data for the paper "A parameter-invariant activity threshold for the erasure of spatial pattern in active Model H" (R. M. Chen). An imposed stripe pattern in a conserved order-parameter field coupled to a Stokes solvent is destroyed by active stress above a critical activity and persists indefinitely below it. The deposit contains everything needed to reproduce that result: a pseudospectral solver for the conserved field with deviatoric active stress, thirteen sweep scripts that call it with different parameters, and trajectory data for the activity sweep. Contents. fidelity_test.py defines the solver used by every result in the paper. The sweep scripts cover the activity sweep and fine bracketing of the threshold, wavelength dependence, the gradient coefficient, the bulk free-energy coefficient, mobility and viscosity, grid spacing and box size, initial pattern amplitude, the passive metastability control, and a Fourier band growth diagnostic. zeta_sweep.json holds 27 runs of the activity sweep: per run the activity, seed, sampled times, fidelity F(t), domain scale L(t), and half-life t50. Reproducing. Each script is self-contained, requires only Python 3 and numpy, is checkpointed, and prints the table that appears in the paper. Runtimes are 40 minutes to 2.5 hours per script on one CPU core. The solver is deterministic with fixed random seeds: a regeneration performed after the manuscript was written reproduced the reported half-lives to the digit (961, 799, 596, 367 and 388 at |ζ| = 1.07, 1.08, 1.10, 1.15 and 1.143). Trajectory files for the remaining sweeps are therefore not included, since they regenerate exactly. Numerical scheme. Pseudospectral on a periodic square, semi-implicit in the stiff κk⁴ term, 2/3 dealiasing, Stokes flow by transverse projection. Reference resolution 128² on a box of side 64, dt = 0.02. Every quantity reported in the manuscript derives from these runs.
DOI: 10.5281/zenodo.22614745
Language: English
Open Access status: green
OpenAlex ID: W7211869313
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